The key advantage of using microservices architecture is its ability to enhance scalability and flexibility in software development. In this approach, applications are built as a collection of loosely coupled services, each handling specific business functions. Such architecture makes it easier to update and deploy individual services independently, reduces the risk of system-wide failures, and allows teams to use different technologies suited for particular services. This modularity also simplifies the process of scaling different components of the application based on varying demand, ultimately leading to better resource utilization and improved performance.